TAHMOOR COLLIERY LONGWALL 24B

Transcription

1 TAHMOOR COLLIERY LONGWALL 24B END OF PANEL SUBSIDENCE MONITORING REPORT FOR LONGWALL 24B AT TAHMOOR COLLIERY Level, 228 Victoria Avenue - Chatswood NSW 23 PO Box 347 Willoughby North NSW 268 Tel. (2) Fax. (2) enquiries@minesubsidence.com REPORT NO. MSEC272-6 February 28

2 DOCUMENT REGISTER Revision Description Author Checker Date Report after 3m of Extraction LW24B PLD DJK Dec 26 2 Report after 5m of Extraction LW24B PLD DJK Jan 27 3 Report after 7m of Extraction LW24B PLD DJK Feb 27 4 Report after 9m of Extraction LW24B PLD DJK Apr 27 5 Report after m of Extraction LW24B PLD DJK May 27 6 End of Longwall Report LW24B DJK DRK Feb 28 Report produced for:- Compliance with conditions attached to the SMP Approval by the Department of Primary Industries Minerals Acknowledgments We would like to acknowledge the extensive contribution provided by various organisations to this report. These organisations have conducted most of the on-ground surveys and inspections. We would particularly like to acknowledge the close dialogue between Tahmoor Colliery and the Mine Subsidence Board, which has ensured a timely and accurate flow of information regarding impacts to structures. We would like to acknowledge the following organisations: Australian Rail Track Corporation Department of Primary Industries Geoterra Hydrometric Consulting Services Lean & Hayward Surveyors Lutibo (Colin Dove) Meadows Consulting Mine Subsidence Board Pidgeon Civil Engineering Sunrise Building and Property Services Sydney Water Tahmoor Colliery References, (24). Tahmoor Colliery Longwalls 24 to 26 Report on the Prediction of Subsidence Parameters and the Assessment of Subsidence Impacts on Surface and sub-surface Features due to Mining Longwalls 24 to 26 at Tahmoor Colliery in support of an SMP Application. Volume. Report No. MSEC57, Revision C, March 26. Geoterra, (27). Xstrata Coal Tahmoor Colliery End of Longwall 24B Surface Water, Dams & Groundwater Monitoring Report, Tahmoor NSW. GeoTerra Report No. TA5-R2A, January 28. Report No. MSEC272-6 February 28 i Xstrata Coal Tahmoor Colliery Longwall 24B End of Panel Report Subsidence Monitoring Report

3 DOCUMENT REGISTER TABLE OF CONTENTS LIST OF DRAWINGS AND ILLUSTRATIONS TABLE OF CONTENTS CHAPTER. INTRODUCTION 4 CHAPTER 2. COMPARISON BETWEEN OBSERVED AND PREDICTED SUBSIDENCE MOVEMENTS Comparison between Predicted and Observed Systematic Subsidence Movements Subsidence Systematic Tilt, Curvature and Strain Summary of Predictions of Systematic Subsidence 2.2. Identification of Non-Systematic Subsidence Movements 2.3. Main Southern Railway Thirlmere Way Overbridge Castlereagh Street Bridge over Myrtle Creek Sewer Surveys Power Pole Surveys Tahmoor Town Centre 5 CHAPTER 3. SUMMARY OF SURVEYS AND INSPECTIONS 6 CHAPTER 4. IMPACTS TO SURFACE FEATURES Summary of Impacts to Surface Features Main Southern Railway Roads Potable Water Infrastructure Gas Infrastructure Sewer Infrastructure Electrical Infrastructure Telecommunication Infrastructure Structures Residential Structures and Public Amenities Swimming Pools Associated Structures Fences 28 CHAPTER 5. SUMMARY OF RESULTS 29 i ii iii Report No. MSEC272-6 February 28 ii Xstrata Coal Tahmoor Colliery Longwall 24B End of Panel Report Subsidence Monitoring Report

4 LIST OF DRAWINGS AND ILLUSTRATIONS Drawings Drawing No. Description Rev MSEC272- Longwall No. 24B Monitoring Lines G MSEC272-2 Longwall No. 24B Impacts BE Figures Figure No. Description MSEC272- Total Subsidence Profiles along Main Southern Railway Corridor Line MSEC272-2 Incremental Subsidence Profiles Main Southern Railway Corridor Line MSEC272-3 Total Subsidence Profiles along Thirlmere Way Line MSEC272-4 Incremental Subsidence Profiles along Thirlmere Way Line MSEC272-5 Total Subsidence Profiles along Chapman Street Line MSEC272-6 Total Subsidence Profiles along Castlereagh Street Line MSEC272-7 Incremental Subsidence Profiles along Castlereagh Street Line MSEC272-8 Total Subsidence Profiles along Park Street Line MSEC272-9 Incremental Subsidence Profiles along Park Street Line MSEC272-2 Total Subsidence Profiles along Milne Street Line MSEC272-3 Incremental Subsidence Profiles along Milne Street Line MSEC272-4 Total Subsidence Profiles along Elphin Street Line MSEC272-5 Incremental Subsidence Profiles along Elphin Street Line MSEC272-6 Incremental Subsidence Profiles along Elphin-Myrtle Creek Line MSEC272-7 Total Subsidence Profiles along Pimelia Street Line MSEC272-8 Incremental Subsidence Profiles along Pimelia Street Line MSEC272-9 Total Subsidence Profiles along Winpara Close Line MSEC272-2 Incremental Subsidence Profiles along Winpara Close Line MSEC272-2 Total Subsidence Profiles along Huen Place Line MSEC Incremental Subsidence Profiles along Huen Place Line MSEC Total Subsidence Profiles along Macquarie Place Line MSEC Incremental Subsidence Profiles along Macquarie Place Line MSEC Total Subsidence Profiles along Turner-Denmead Line MSEC Incremental Subsidence Profiles along Turner-Denmead Line MSEC Total Subsidence Profiles along Brundah Road Line MSEC Incremental Subsidence Profiles along Brundah Road Line MSEC Total Subsidence Profiles along Marion Street Line MSEC272-3 Incremental Subsidence Profiles along Marion Street Line Report No. MSEC272-6 February 28 iii Xstrata Coal Tahmoor Colliery Longwall 24B End of Panel Report Subsidence Monitoring Report

5 CHAPTER. INTRODUCTION This report has been prepared by Pty Ltd (MSEC) for Xstrata Coal Tahmoor Colliery to comply with conditions of the SMP Approval by the Department of Primary Industries, particularly portions of Clause 3. This report compares the observed and predicted subsidence, tilt and strain profiles along all available monitoring lines, and the observed and predicted impacts on surface features, following the completion of Longwall 24B. The location of Longwall 24B is shown in Drawing No. MSEC272-, which together with all other drawings, is attached in Appendix A at the back of this report. This report also includes many of the movements and impacts observed during the extraction of Longwalls 22 to 24B. The dates of extraction for all longwalls are provided in Table.. Table. Start and Finish Dates for Longwalls 22 to 24B Longwall Start Date Completion Date Longwall 22 3 May July 25 Longwall 23A 3 September 25 2 February 6 Longwall 23B 22 March August 26 Longwall 24B 4 October 26 2 October 27 Longwall 24A 5 November 27 Current longwall The predicted movements and impacts resulting from the extraction of Longwalls 24 to 26 were provided in Report No. MSEC57 (Revision C), which was issued in March 26. Longwall 24B was approximately 226 metres long and 283 metres wide, rib to rib. The pillar width was approximately 34.5 metres wide, rib to rib. The depth of cover was relatively consistent over the panel, varying between 43 and 44 metres. While the seam thickness varied between.75 metres at the finishing end and 2.5 metres at the commencing end, Tahmoor Colliery advised that the design cut for Longwall 24B was 2.5 metres and the shearer would never cut below 2.5 metres. Chapter 2 of this report describes the monitoring lines and monitoring points at Tahmoor Colliery, and provides comparisons between the observed and predicted movements resulting from the extraction of Longwall 24B. Chapter 3 of this report summarises the surveys and inspections undertaken during the mining of Longwall 24B. Chapter 4 of this report describes the reported impacts on surface features resulting from the extraction of Longwall 24B, and compares these with the predicted impacts. The reported impacts on surface water and ecology are provided in other reports. Appendix A includes all drawings and figures associated with this report. 4 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

6 CHAPTER 2. COMPARISON BETWEEN OBSERVED AND PREDICTED SUBSIDENCE MOVEMENTS As set out in the Surface Safety and Serviceability Management Plan, for Tahmoor Colliery Longwalls 24 to 26, regular subsidence surveys have been conducted along monitoring lines that have been established in selected streets. The monitoring is being undertaken to compare observed movements against predicted movements, and to identify any anomalous movements that might potentially have an adverse effect on surface features. The locations of all of the monitoring lines near Longwall 24B are shown in Drawing No. MSEC272-. In addition to the monitoring lines, subsidence monitoring was conducted at survey stations located at and around the Tahmoor Town Centre, road bridges and culverts, and selected power poles in accordance with the Surface Safety and Serviceability Management Plan. Surveys were also undertaken at houses that form part of a research project that was developed between the Department of Primary Industries and Tahmoor Colliery during the mining of Longwalls 22 and 23. Surveys were undertaken at regular intervals during the extraction of Longwall 24B and the End of Panel surveys were conducted during October to December 27. The observed total and incremental subsidence profiles along the monitoring lines are provided in Figs. MSEC272- to MSEC Comparison between Predicted and Observed Systematic Subsidence Movements 2... Subsidence Review of the magnitude of the observed subsidence A comparison of maximum observed and predicted subsidence due to and after the mining of Longwall 24B is provided in Table 2.. Table 2. Summary of Maximum Predicted and Observed Subsidence Maximum Incremental Subsidence due to LW 24B (mm) Maximum Total Subsidence after LW 24B (mm) Predicted (SMP Report MSEC57) Nearest Street Location Observed 65 Patterson Street Thirlmere Way 89 Monitoring Line Huen Place extension north of Myrtle Creek A house on Thirlmere Way (not identified for privacy reasons) It can be seen from Table 2. that observed maximum incremental subsidence was slightly greater than predicted maximum subsidence. The difference is 24 mm, which is very small and represents an underprediction of approximately 4 %. As noted in the SMP Report No. MSEC57, empirical methods of subsidence prediction are generally accepted as providing predictions of maximum subsidence to an accuracy of ± % to ± 5% (please refer to Section 3.25 of Report No. MSEC57). It can also be seen from Table 2. that observed maximum total subsidence is less than predicted maximum subsidence. The difference is approximately 47 mm, which is very small and represents an over-prediction of approximately 5 %. One reason for this slight under-prediction follows from using a seam thickness range of.75 to 2.5 metres for the prediction calculations for Longwall 24B, as per the seam thickness drawing in the SMP Report (Drawing No. MSEC57-8), whilst Tahmoor Colliery has since advised that the shearer never cuts below 2.5 metres and the design cut height is 2.5 metres. This represents a 7 to 23% increase in cutting height at the north-eastern end of Longwall 24B and this would have resulted in an increase in predicted subsidence and over-predictions rather than under-predictions. While the predictions of maximum subsidence are within the stated accuracy of the Incremental Profile Method, it is recognised that subsidence is not measured across the whole subsided area. It is therefore 5 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

7 likely that there are areas that have experienced subsidence that is slightly greater than the maximum measured. However, given the density of the monitoring grid, it is likely that any difference from the maxima reported in this report will be small. The following detailed comparisons between the observed and predicted subsidence are presented without adjusting for this increase in extracted seam thickness. A summary of maximum observed and predicted subsidence along each monitoring line is provided in Table 2.2. Table 2.2 Summary of Maximum Subsidence along Monitoring Lines MONITORING LINE Main Southern Railway MAXIMUM INCREMENTAL SUBSIDENCE DUE TO EACH LONGWALL LW22 (mm) MAXIMUM TOTAL SUBSIDENCE AFTER EACH LONGWALL OBSERVED PREDICTED OBSERVED PREDICTED LW23A & LW23B (mm) LW24B (@ m) (mm) LW24B (mm) LW22 (mm) LW23A & LW23B (mm) LW24B (@ m) (mm) LW24B (mm) Thirlmere Way Chapman Street Castlereagh Street Park Street Fraser Street Milne Street Elphin Street Elphin-Myrtle Creek Pimelia Street Winpara Close Huen Place Macquarie Place Turner-Denmead Brundah Road Marion Street All Monitoring Lines Testing of the Incremental Profile Method against Tahmoor Colliery surveys was undertaken prior to the SMP submission and the results were provided in the SMP Report No. MSEC57. Based on observations from previous Tahmoor panels including Longwalls 22 and 23A, predicted maximum incremental subsidence was set to approximately 9 % of the standard Incremental Profile Method. The results from Longwalls 22 and 23A were graphically presented in Fig. 3. of the SMP Report. This graph has been reproduced in Fig. 2., with the results for Longwalls 23B and 24B included. 6 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

8 It can be seen from Fig. 2. and Table 2.2 that observed maximum incremental subsidence is greater than predicted maximum incremental subsidence for all monitoring lines. Where subsidence is predicted at points beyond the goaf edge, which are likely to experience very low values of subsidence, the predictions should generally be accurate to within 5 mm of subsidence, which has been observed here. When compared to the experience from previous longwalls, observed subsidence has been comparatively greater, though the difference is still within ± 5% in the majority of cases. Considering that the extracted height was up to 23% greater than the seam thickness adopted for the predictions in the SMP Report, this comparison indicates that the predicted subsidence values are generally reasonable. Measured Maximum Incremental Subsidence (mm) Marion Elphin-Myrtle Milne Railway Longwall 22 Longwall 23A & 23B Longwall 24B I:\Projects\Tahmoor\SurveyData\Tahmoor North Overall\Comparison Max Inc Subs LW22.grf Turner-Denmead Park Brundah Winpara Castlereagh Castlereagh Milne Fraser Thirlmere Castlereagh Pimelia Market Milne Macquarie Byron-Bronzewing Byron-Bronzewing Turner-Denmead Railway Brundah Railway Influenced by igneous intrusion and coal barrier (LW23A/B) Huen Elphin Chapman : Relationship Macquarie Place Turner-Denmead Thirlmere Market Fraser Fraser Thirlmere As stated in SMP Report No. MSEC57, prediction of maximum subsidence over a panel should be accurate to ± 5%. Accuracy of prediction at a point is more difficult than ± 5% but should be generally conservative. At low levels of subsidence, predictions should be accurate to 5 mm of subsidence. Area shown is ± 5 mm or 5% of predicted movement, whichever is greater Predicted Maximum Incremental Subsidence (mm) Fig. 2. Comparison between Measured and Predicted Maximum Incremental Subsidence above Longwalls 22 to 24B at Tahmoor Colliery As shown in Fig. 2. and Figs. MSEC272- to MSEC272-3, a very good correlation between observed and predicted incremental subsidence was observed on many monitoring lines. These include Thirlmere Way, Chapman Street, Fraser Street, Pimelia Street, Winpara Close and Turner-Denmead and Marion Street. While the correlation between observed and predicted subsidence was exceptional for these monitoring lines, we would prefer, in principle, to provide predictions that are more conservative than observed subsidence. The locations of greatest exceedence of subsidence predictions are in the vicinity of the coal barrier between Longwalls 23A and 23B, such as Macquarie Place, Huen Place, Milne Street, Fraser Street and a section along Thirlmere Way above Longwall 22. The results are most evident along the Elphin Street and the Huen Place extension line, which crossed Myrtle Creek. The amount of exceedence at the Huen Place extension was approximately 5 mm, which represents an under-prediction of approximately 22 %. The amount of exceedence along Elphin Street was approximately 8 mm, which represents an 7 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

9 under-prediction of approximately 6 %. The potential for less favourable correlation between observed and predicted subsidence was anticipated at the time of writing the SMP Report No. MSEC57 (please refer Section 3.27) as irregular, non-systematic subsidence movements were observed in the vicinity of the igneous intrusion during the mining of Longwalls 22 and 23A. There is also limited empirical information available on subsidence movements around coal barriers. These exceedences would have been reduced if the minimum extraction heights of 2.5 metres or the design cutting height of 2.5 metres had been adopted for the SMP predictions. For example, observed maximum subsidence along Brundah Road exceeded predictions by approximately 3.4% and the seam thickness directly below this monitoring line was approximately.8 metres. If the actual extracted height was 2.5m, we would add 3.9% additional subsidence to the predictions. If the actual extracted height was the design cut of 2.5m, we would add 9.4% to the predictions. However, even if some predictions were adjusted for increased extraction heights, observed incremental subsidence due to the mining of Longwall 24B would nevertheless have been greater than predicted subsidence in some areas, such as along Park Street. The amount of exceedence was almost uniform along the whole length of this monitoring line, as shown in Fig. MSEC Maximum observed subsidence was greater than predicted maximum subsidence by approximately 59 mm, which represents an under-prediction of approximately 2 %. The seam thickness directly beneath Park Street is approximately 2. metres. If the actual extracted height was 2.5m, we would add 2.5% additional subsidence to the predictions. If the actual extracted height was the design cut of 2.5m, we would add 7.5% to the predictions. Review of Subsidence Profile Shapes There was generally a reasonable correlation between the shapes of the predicted and observed subsidence profiles, as shown by Figs. MSEC272- to MSEC Some observed profiles compare vey well with predicted profiles, such as Thirlmere Way, Chapman Street, Park Street, Elphin Street, Elphin-Myrtle Creek, Pimelia Street and Winpara Close. The correlation between observed and predicted profile shapes were less favourable for all sections of monitoring lines near the coal barrier between Longwalls 23A and 23B, which was anticipated for the reasons discussed already. The correlation between observed and predicted profile shapes was also less favourable where the monitoring lines traverse the sides of the longwall panel where the subsidence profiles are steepest. This was observed, for example along Castlereagh Street above the commencing end of Longwall 23A and increased subsidence was again observed at this location during the mining of Longwall 24B. Summary Observed subsidence was comparatively greater than predictions in the SMP Report, unlike previous observations during the mining of Longwalls 22 and 23. The difference between observed and predicted subsidence was, however, generally within the stated accuracy of the prediction method. Observed and predicted subsidence was very close for many monitoring lines. However, we would prefer, in principle, to provide predictions that are more conservative. The extraction heights have been greater than adopted in the SMP Report and the predictions would have been increased in some cases. The greatest departures between observed and predicted subsidence were located in the vicinity of the igneous intrusion and coal barrier between Longwalls 23A and 23B, which was anticipated at the time of writing the SMP Report. Finally, it was found that there was generally a reasonable correlation between observed and predicted systematic subsidence profiles. This means that there has been a good correlation between predicted and observed differential movements (particularly tilt and curvature). This is an important observation as subsidence impacts generally occur as a result of differential movements rather than absolute vertical subsidence. Further details in differential subsidence movements are provided in the following section. 8 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

10 2..2. Systematic Tilt, Curvature and Strain Observed maximum tilts, curvature and strain have generally been less than predicted systematic tilts, curvature and strain throughout Longwall 24B. In a small number of isolated locations, observed tilt, curvature and strain have exceeded the systematic predictions but it is clear that non-systematic movement has occurred in each of these instances. Predictions and discussion on non-systematic movement were provided separately in the SMP Report and discussion on observed non-systematic movements are provided in the Section 2.2 of this report. Maximum predicted incremental systematic tilt for Longwall 24B was predicted to be 4.7 mm/m. As shown in Figs. MSEC272- to MSEC272-3, observed tilt was less than predicted maximum tilt along all of the monitoring lines where systematic subsidence has occurred. Maximum observed incremental systematic tilt was approximately 4.3 mm/m, which occurred along Chapman Street. Maximum observed tilt exceeded the prediction maximum systematic tilt in one instance along the monitoring lines, and this occurred along Brundah Road (5.7 mm/m), where non-systematic movement had clearly occurred. It is not surprising that observed tilts have been consistently less than the predicted maximum tilt as the monitoring lines are generally orientated at 45 degrees to the longwalls. The predicted maximum tilt is oriented transverse to the longwalls. The main exception is Chapman Street, which though orientated at an angle of 45 degrees to the longwalls, is located directly above the corner of Longwall 24B. It is therefore not surprising that maximum observed tilt was measured on this monitoring line. A more accurate method of comparing observed and predicted tilts can be achieved by comparing observed and predicted tilt profiles, which are shown in Figs. MSEC272- to MSEC It can be seen from these results that there is a reasonable correlation between observed and predicted systematic tilt, especially when the increased extraction height is considered. At most locations, the difference between observed and predicted tilt is comfortably less than mm/m. Maximum predicted incremental systematic radii of curvature for Longwall 24B were predicted to be. km - sagging and.5 km - hogging. While not shown graphically in this report, observed curvature was equal to or less than predicted maximum curvature along all of the monitoring lines where systematic subsidence has occurred. Maximum observed incremental systematic curvature was approximately.8 km - sagging and.5 km - hogging, which occurred along Chapman Street. In all instances where maximum observed strain exceeded the predicted maxima, non-systematic movement had occurred. Maximum observed non-systematic incremental curvature of.8 km - sagging and.9 km - hogging occurred on Brundah Road. Maximum predicted incremental systematic strain for Longwall 24B was predicted to be.8 mm/m tensile and.5 mm/m compressive. As shown in Figs. MSEC272- to MSEC272-3, observed strains were equal to or less than predicted maximum strains along all of the monitoring lines where systematic subsidence has occurred. Maximum observed incremental systematic tensile strain was approximately.8 mm/m on Brundah Road. Maximum observed incremental systematic compressive strain was approximately. mm/m on Park Street. In all instances where maximum observed strain exceeded the predicted maxima, non-systematic movement had occurred. Maximum observed non-systematic incremental compressive strain of 4.2 mm/m occurred on Brundah Road. Interestingly, a previously identified site of non-systematic movement on Milne Street experienced a relaxation of compressive strain of.9 mm/m during the mining of Longwall 24B. Further details on non-systematic movement are provided in Section Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

11 2..3. Summary of Predictions of Systematic Subsidence In summary, there is generally a good correlation between observed and predicted systematic subsidence, tilt, curvature and strain due to the mining of Longwall 24B. We recommend that predictions of systematic subsidence remain unchanged from those provided in the SMP Report No. MSEC57 for Longwalls 25 and 26 for the following reasons: Observed maximum incremental subsidence is within 4% of predicted maximum incremental subsidence, which is within the stated accuracy of ± % to ± 5%. Observed maximum total subsidence after Longwall 24B is less than predicted maximum total subsidence by approximately 5%. There is a reasonable correlation between observed and predicted shapes of subsidence and tilt profiles. Observed tilt, curvature and strain is less than predicted maxima where systematic subsidence has occurred. Subsidence due to Longwall 24B is significantly influenced by the presence of the large igneous intrusion and coal barrier located between Longwalls 23A and 23B, where most notable departures from predicted subsidence were observed. Actual extraction heights are slightly greater than assumed in the SMP Report, particularly at the finishing end of the longwalls. Other notable departures between observed and predicted tilt, curvature and strain occurred where non-systematic movements have occurred. While non-systematic movements were anticipated, predictions and discussion of these types of movements were treated separately in the SMP Report and do not form part of this review of predicted systematic subsidence. There is a reasonable correlation between observed and predicted impacts, which is discussed in CHAPTER 4. The methods adopted by Tahmoor Colliery to manage potential subsidence impacts would not change as a result of any slight adjustment to predicted subsidence. While slight adjustments could be made to subsidence predictions in the interests of providing more conservative predictions, such changes would potentially generate unnecessary and unwarranted confusion within the community. However, based on this experience we intend to adjust the prediction method for future SMP applications to be more conservative Identification of Non-Systematic Subsidence Movements Irregular subsidence movements can be found in observed subsidence, tilt and strain profiles. The most common causes of irregular movements in subsidence profiles are listed below. Valley closure and upsidence, Geological structures, Change in direction of monitoring line, Bumped or damaged pegs, Survey line discontinuities, where survey lines are extended after the subsidence has already occurred, Survey inaccuracies, and Anomalous movements Irregularities that have occurred as a result of the surveying process are not considered to be non-systematic subsidence movements. Anomalous movements have been identified by a process of elimination. If a cause behind an irregularity in a subsidence, tilt or strain profile cannot be explained, the irregularity is described as an anomaly. Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

12 There are twelve new locations where it is considered that non-systematic movement has occurred in the period during the mining of Longwall 24B. Other non-systematic movements were identified during the extraction of Longwalls 22 to 23, however there has been little change to these movements during the mining of Longwall 24B. A summary of new non-systematic movements for the monitoring lines within the active subsidence zone is provided below in Table 2.3. Table 2.3 Location of New Identified Non-Systematic Movements during Longwall 24B Monitoring Line or Location Brundah Road (Pegs BH9-2) Brundah Road (Pegs BH25-26) Brundah Road (no survey line) Elphin Street (Pegs E8-) Elphin-Myrtle (Pegs EM3-6) Huen Place (Pegs H8-4) Maximum Upsidence (mm) Maximum Strain (mm/m) Maximum Tilt (mm/m) Type Anomaly Impacts to Surface Pavement and one house Anomaly Pavement Not measured Not measured Not measured Anomaly Anomaly (4 m bay) -4.6 (4 m bay) -2.3 (8 m bay) -3.5 (9 m bay).9 Valley None 4.5 Valley None Glenanne Place Not measured Not measured Not measured Anomaly Mahonga Street Not measured Not measured Not measured Anomaly Pimelia Street (Pegs PM2-4) Reserve between Stuart and Huen Place House at Turner Street Winpara Close (Pegs W2-5) Impact to pavement and one house beyond goaf edge Possibly minor impacts to house Localised impacts to pavement, fence, water main and house Impacts at two houses at low levels of subsidence and early longwall progress Anomaly Kerb and gutter Not measured Not measured Not measured Nil on Turner- Denmead Line Valley or Anomaly -. to Anomaly Anomaly Impacts to all houses backing onto Reserve Impact to one house only well beyond goaf edge Impacts to road surface and irregular impacts to kerb and gutter. In this table, upsidence is defined as the height of the local subsidence bump at the anomaly, as calculated or determined from an otherwise smooth systematic subsidence profile. The maximum upsidence at these anomalies is 45 mm, which is small relative to the observed total subsidence of 89 mm. Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

13 Further details are provided below with regards to some of the newly identified locations of non-systematic movement. Anomalous movements have been observed in two locations along Brundah Road. The movements were first apparent following the 9 metre survey. The movements have resulted in impacts to the road pavement, which are shown in Fig. 4.. Relative level surveys around a nearby house indicate a lifting of the walls and slab in one corner. The slab feels uneven and slippage has occurred to the damp proof course in this same corner. One sewer pipe has also experienced reverse gradient and had to be re-laid. It is therefore considered that this house has also experienced anomalous non-systematic movements. Four impacts were observed in close proximity on Glenanne Place. Longwalls 22 to 24B have directly mined beneath over 2 kilometres of water main pipework and this is the only site to have experienced impacts. In addition to this, the road pavement cracked and buckled at the same localised location, as did some timber rails on a fence, and minor impacts were experienced in a nearby house. While no ground surveys have been conducted along this street, the nature of the impacts suggest significant anomalous movements. A photograph of impacts to the pavement is shown in Fig. 4.. The Mine Subsidence Board has received claims from almost every property that backs onto Stuart Reserve. The properties are located on Stuart and Huen Place. Some of the impacts to the houses are categorised as Category 3 and one house, which backs onto Myrtle Creek has experienced Category 4 impacts. Given that all of these houses are located above the igneous intrusion and coal barrier between Longwalls 23A and 23B, it is considered that the impacts are related to non-systematic movement. The cause or causes of the impacts are not known but there are a number of possibilities. Stuart Reserve is located within a natural drainage line that flows into Myrtle Creek and it is possible that the structures have experienced valley related movement. It is also not known whether part of the drainage line had been backfilled as part of sub-division work and whether this may have influenced movements at the structures. These impacts could also have been affected by the presence of the igneous intrusion. Unfortunately, there is no monitoring line available to measure the ground movements that occurred. A number of monitoring lines are located above the igneous intrusion and very little differential movement was observed. No non-systematic movement has observed along these lines, which include a short monitoring line across the top of the drainage line at Stuart Place. Valley closure and upsidence movements have been observed along Myrtle Creek, as expected. Monitoring lines were placed across the creek near Huen Place and Elphin Street for research purposes. Valley closure movements were first observed following the 9 metre survey. The observed peak compressive strains are aligned with the base of Myrtle Creek. Upsidence movements are less evident than the valley closure related compressive strains. In the case of the Huen Place extension line, upsidence is difficult to distinguish due to the timing of the extension of the ground survey across Myrtle Creek. Non-systematic movement along the Winpara Close monitoring line was first observed following the 9 metre survey. The profiles for Winpara Close show some minor upsidence which has developed slightly since the metre survey. The movements have results in irregular surface impacts to the pavement and kerb and gutter and a photograph is shown in Fig. 4.. Two houses on Mahonga Street experienced impacts on 7 and 3 November 26. Longwall 24B had progressed distances of approximately 24 metres and 32 metres respectively at this time. The impacts to one house are significant and include cracking to brickwork, cracking and delamination of floor tiles and jamming of doors. The impacts are considered to be a result of anomalous non-systematic movement due to the early timing of the impacts. 2 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

14 A house on Turner Street has reported impacts during the mining of Longwall 24B. The house is located a minimum distance of 7 metres from the nearest goaf edge. A claim at this distance is unusual, as evidenced by the impacts map, which is provided in Drawing No. MSEC A recent inspection of the house indicates movement along the damp proof course, cracking and spalling of brick mortar, cracking of external concrete pavement and cracking of linings to internal walls and ceiling. The house is located directly above an area identified as geologically disturbed at seam level and it is not known whether these conditions extend to the surface. The impact is perplexing in that neither the road, kerb nor any other neighbouring houses have experienced impacts. However, in the absence of any other cause, it is assumed that the impact is related to mine subsidence given the timing of the impact. In addition to the above locations, it is possible that there are other sites are experiencing non-systematic movement. These include the noticeable hump in the pavement on Leiha Place and small strain concentrations and upsidence along the Main Southern Railway. The locations of all sites where it is considered that observed non-systematic movements have occurred are shown in Drawing No. MSEC Main Southern Railway The Main Southern Railway was surveyed 22 times on a weekly, twice weekly and thrice weekly basis during the extraction of Longwall 24B. The Main Southern Railway experienced 88 mm of subsidence during the mining of Longwall 24B, which is also the maximum total subsidence experienced due to the mining of Longwalls 22 to 24B. While observed subsidence was slightly greater than predicted, the difference was well within the accuracy of the prediction method. Observed maximum incremental and total tilts were less mm/m. Observed maximum incremental strain was approximately.4 mm/m compressive and observed maximum total strain was.6 mm/m compressive. No anomalous movements were observed during mining though a number of small bumps and localised compressive strains have occurred at some isolated locations, which will be closely watched in case they develop into significant anomalous movement during the extraction of Longwall 25. Observed changes in stress free temperature in the rails was 7 degrees, which is less than the predicted change of 8 degrees. It was found that continuous monitoring of rail strain gauges and rail temperature provided a valuable tool for monitoring welded track stability during mining. A very good correlation was found between observed ground strain, subsidence and changes in stress free temperature throughout the mining period. Platform clearances at Tahmoor Railway Station were measured in accordance with the agreed management plan with Australian Rail Track Corporation (ARTC) and measured changes in clearances were within survey tolerance. Since the completion of mining Longwall 24B, ARTC has subsequently upgraded both the Up and Down Tracks from timber to concrete sleepers and the track and platform has subsequently been adjusted Thirlmere Way Overbridge A total of 2 surveys and 4 visual inspections were undertaken of the Thirlmere Way Overbridge on a weekly basis in accordance with the agreed management plans with ARTC and Wollondilly Council. No impacts were observed to the Bridge, as expected following extensive strengthening works undertaken by Tahmoor Colliery prior to commencement of Longwall 24B. Maximum subsidence of 73 mm was measured at the Bridge. Maximum tilt of.8 mm/m was measured across the deck, falling towards Longwall 24B on the Thirlmere side of the bridge. Measured strains were within survey accuracy. The expansion joint was measured on 4 occasions and the results were always within 2 mm of the initial survey. A survey of the bridge opening above the Main Southern Railway track was conducted and the results show that the bridge opening satisfies Structure Gauge requirements. 3 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

15 2.5. Castlereagh Street Bridge over Myrtle Creek A total of 4 surveys were undertaken of the Castlereagh Street Bridge over Myrtle Creek in accordance with the agreed management plan with Wollondilly Council. No impacts were observed to the Bridge, as expected. Maximum subsidence of 58 mm has been measured at the bridge. The bridge has subsided in a relatively uniform fashion with negligible tilts and strains Sewer Surveys A total of 28 surveys along two sewer pipes that cross Myrtle Creek were conducted on a weekly and twice weekly basis in accordance with the agreed management plan with Sydney Water. No impacts were observed to any sewer infrastructure during the mining of Longwall 24B. I:\Projects\Tahmoor\SurveyData\Myrtle Creek\Sewer Crossing\Sewer Crossing.grf LONGWALL 24B COMPLETE 225 MM DIA SEWER MAINS Standard Spigot & Socket Horizontal Bore Concrete Encased Sewer LONGWALL 23B BRIDGE ST Myrtle Creek Creek Crossing Change in grade (%) ve Increase in grade -ve Reduction in grade Huen Pl Brundah Rd MILNE ST HUEN PL PARK ST WINPARA CL FRASER ST PIMELIA ST ELPHIN ST MONICA PL LEIHA PL AMBLECOTE PL CASTLEREAGH ST HILTON PARK RD CONNOR PL SP45 MAIN SOUTHERN RWY Strain (mm/m) Closure between sewer pits (mm) Fig Longwall 24B Face Distance (m) Observed Strain and Closure along Sewer Pipes that cross Myrtle Creek 4 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

16 In accordance with the management plan, daily visual inspections were conducted once observed closures exceeded 2 mm. A total of 28 visual inspections were made during mining. While no impacts were recorded during mining, the observed amount of closure in the pipes is significant and it is possible that impacts may be experienced during the mining of Longwall 25. It is recommended that Tahmoor Colliery consider implementing measures to prevent this potential impact Power Pole Surveys A total of 46 surveys of selected power poles were conducted in accordance with the agreed management plan with Integral Energy. No impacts were observed to any power pole during the mining of Longwall 24B as expected. Of the poles that were surveyed, maximum subsidence of 623 mm was observed at Pole 27 on Glenanne Place. A maximum horizontal movement of 4 mm was measured at the top of the same pole in May 27. The amount of movement reduced to 23 mm at the completion of Longwall 24B Tahmoor Town Centre Four detailed surveys of the Tahmoor Town Centre and basement carpark were undertaken in accordance with the conditions of SMP Approval by the Department of Primary Industries. No impacts were observed to Tahmoor Town Centre during the mining of Longwall 24B as expected. Maximum observed subsidence was mm, which is within prediction, which was less than 2 mm of subsidence. 5 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

17 CHAPTER 3. SUMMARY OF SURVEYS AND INSPECTIONS Many surveys and inspections were required to be conducted to meet the requirements of the Surface, Safety and Serviceability Management Plan. Due to the complexities involved, surveys and inspections were managed using a computer database on a weekly basis. A register was also kept, detailing when each survey and inspection had been completed. A timeline showing when each type of survey and inspection was conducted is shown in Fig. 3. and Fig I:\Projects\Tahmoor\MSEC272 - Monitoring LW24B\Subsdata\Survey and Inspection Timelines LW24B.grf Oct-6 Nov-6 Dec-6 Jan-7 Feb-7 Mar-7 Apr-7 May-7 Jun-7 Jul-7 Aug-7 Sep-7 Oct-7 Nov-7 Main Southern Railway Corridor Thirlmere Way Chapman St Castlereagh St Park St Milne St Elphin St Elphin-Myrtle Ck Pimelia St Winpara Cl Huen Pl Macquarie Pl Turner-Denmead Sts Brundah Rd Marion St Bargo River Flow Gauging Bargo River Data Logger Downloads Bargo River Water Level Surveys Bargo River Water Quality Sampling Myrtle Ck Visual Monitoring Myrtle Ck Data Logger Downloads Myrtle Ck Water Quality Sampling - Field Myrtle Ck Water Quality Sampling - Lab Redbank Ck Data Logger Downloads Redbank Ck Water Quality Sampling - Field Redbank Ck Water Quality Sampling - Lab Steep Slopes Visual Monitoring Groundwater Water Levels Groundwater Water Quality Sampling - Field Groundwater Water Quality Sampling - Lab Reports for Monitoring Results Subsidence reports for Railway Enhanced Track Patrol Thirlmere Way Overbridge surveys Thirlmere Way Overbridge Inspections Ground Monitoring Surveys Natural Features Main Southern Railway LW 24B LW 24B Oct-6 Nov-6 Dec-6 Jan-7 Feb-7 Mar-7 Apr-7 May-7 Jun-7 Jul-7 Aug-7 Sep-7 Oct-7 Nov-7 Fig. 3. Timeline and Surveys and Inspections during Longwall 24B (Part of 2) 6 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

18 I:\Projects\Tahmoor\MSEC272 - Monitoring LW24B\Subsdata\Survey and Inspection Timelines LW24B - 2.grf Oct-6 Nov-6 Dec-6 Jan-7 Feb-7 Mar-7 Apr-7 May-7 Jun-7 Jul-7 Aug-7 Sep-7 Oct-7 Nov-7 Castlereagh St Bridge Survey Bridge St Culvert Visual Inspection Bridge St Culvert Survey Myrtle Ck Daily Visual Inspections Myrtle Ck Sewer Crossing at Bridge St Myrtle Ck Sewer Crossing at Huen Pl Choke Report Power Pole Surveys Telstra Visual Inspections Building Surveys Visual Inspections Public Amenities / Commercial District Houses Pools and pool gates Dams Aged Units Bridges and Culverts Sydney Water - Sewer Integral Energy - Electrical Telstra - Telecommunications Tahmoor Town Centre Structure Inspections LW 24B LW 24B Oct-6 Nov-6 Dec-6 Jan-7 Feb-7 Mar-7 Apr-7 May-7 Jun-7 Jul-7 Aug-7 Sep-7 Oct-7 Nov-7 Fig. 3.2 Timeline and Surveys and Inspections during Longwall 24B (Part 2 of 2) 7 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

19 A count of surveys and inspections is provided in Table 3.. Table 3. Number of Surveys and Inspections conducted during Longwall 24B Inspection / Survey Responsibility Number of Inspections / Surveys Ground Monitoring Surveys Main Southern Railway Corridor Meadows Consulting 22 Thirlmere Way Lean & Hayward 7 Chapman Street Lean & Hayward 3 Castlereagh Street Lean & Hayward 4 Park Street Lean & Hayward 6 Milne Street Lean & Hayward 6 Elphin Street Lean & Hayward 9 Elphin-Myrtle Creek Lean & Hayward 5 Pimelia Street Lean & Hayward 5 Winpara Close Lean & Hayward 5 Huen Place Lean & Hayward 6 Macquarie Place Lean & Hayward 3 Turner-Denmead Lean & Hayward 3 Brundah Road Lean & Hayward 2 Marion Street Lean & Hayward 3 Natural Features Sub-Total 5 Bargo River flow gauging HCS 3 Bargo River data logger downloads HCS 3 Bargo River water level surveys HCS 3 Bargo River water quality sampling - field & lab Myrtle Creek - Monthly Visual Monitoring in ASZ + End of LW Myrtle Creek - Download Level Data Loggers (bi-monthly) Myrtle Creek - Water Quality sampling - Field (bi-monthly) Myrtle Creek - Water Quality Sampling - Lab (quarterly) Redbank Creek - Download Level Data Loggers (bi-monthly) Redbank Creek - Water Quality sampling - Field (bi-monthly) Redbank Creek - Water Quality Sampling - Lab (quarterly) Geoterra 2 Sunrise 5 Geoterra 7 Geoterra 7 Geoterra 4 Geoterra 5 Geoterra 7 Geoterra 7 Steep Slopes - Weekly Visual Geoterra 6 8 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

20 Inspection / Survey Responsibility Number of Inspections / Surveys Kerbside Inspection in ASZ Groundwater - Water levels in piezometers (bi-monthly) Groundwater - Water Quality sampling - Field (bi-monthly) Groundwater - Water Quality Sampling - Lab (quarterly) Geoterra 7 Geoterra 7 Geoterra 4 Bargo River data logger downloads Geoterra 3 Main Southern Railway (note Corridor survey above) Reports for continuous discrete rail stress transducers monitoring results Sub-Total 27 Pidgeon Civil Engineering 3 Subsidence monitoring reports MSEC Enhanced track patrol ARTC 25 Thirlmere Way Overbridge surveys Meadows Consulting 3 Thirlmere Way Overbridge inspections Bridges & Culverts Sunrise 4 Castlereagh St Bridge - survey Lean & Hayward 2 Bridge St (Tahmoor) Culvert - visual inspection Bridge St (Tahmoor) Culvert - survey Sydney Water - Sewer Myrtle Creek - daily visual inspections Myrtle Creek - twice weekly survey of sewer crossings at Bridge St (Tahmoor) Myrtle Creek - twice weekly survey of sewer crossings at Huen Place Sunrise 76 Lean & Hayward 3 Sunrise 28 Lean & Hayward 28 Lean & Hayward 28 Choke report from Sydney Water Sydney Water 2 Integral Energy - Electrical Power Pole surveys Lean & Hayward 46 Telstra - Telecommunications Visual inspections Lutibo (Colin Dove) 24 Tahmoor Town Centre Building surveys Lean & Hayward 4 Structure Inspections Public amenities / commercial district Sunrise 33 9 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

21 Inspection / Survey Responsibility Number of Inspections / Surveys Houses, Units and Aged Care Villages Sunrise 248 Pools and pool gates Sunrise 6 Dams Geoterra Sub-Total Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

22 CHAPTER 4. IMPACTS TO SURFACE FEATURES 4.. Summary of Impacts to Surface Features A comparison between predicted and observed impacts to surface features is summarised in Table 4. below. It can be seen from that the impacts to surface features have been relatively minor. The predicted and observed impacts to surface features compare reasonably well, with the exception of locations where non-systematic movements have occurred. Table 4. Summary of Predicted and Observed Impacts during Longwall 24B SURFACE FEATURE PREDICTED IMPACTS OBSERVED IMPACTS NATURAL FEATURES Myrtle Creek Aquifers or Known Groundwater Resources Steep slopes Potential cracking in creek bed. Potential surface flow diversion. Potential reduction in water quality during times of low flow. Potential increase in ponding. Please refer report by Geoterra. Potential soil slippage and cracking to slopes. Large-scale slope failures unlikely. No impacts observed during Longwall 24B. Please refer report by Geoterra. Water depressurisation observed in water bores. Please refer report by Geoterra. No impacts observed during Longwall 24B. Natural Vegetation No impacts anticipated. No impacts observed during Longwall 24B. PUBLIC UTILITIES Railways Roads (All Types) Bridges Water Pipelines Gas Pipelines 8 degree loss of rail stress free temperature. No impact to track geometry likely if systematic movements occur. Minor cracking and buckling may occur in isolated locations. Impacts unlikely due to mining of Longwall 24B. Minor impacts possible to pipelines, particularly older cast iron pipes with lead joints. Ground movements unlikely to adversely impact pipelines if systematic movement occurs. Observed loss of rail stress free temperature of 7 o C. Rail restressed. No impact to track geometry. Cracks and buckling in pavements observed in 7 isolated locations (Glenanne Pl, Brundah Road (3 locations), Winpara Cl, Elphin St, and Leiha Pl). Cracks and buckling observed in concrete kerbs in isolated locations (Castlereagh St, Chapman St, Patterson St, Park St, Elphin St, Pimelia St, Winpara Cl, Huen Pl and Leiha Pl). No impacts observed during Longwall 24B. Leak at cast iron water main on Glenanne Pl, most likely as a result of non-systematic movement. No impacts observed during Longwall 24B. 2 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

23 Table 4. Summary of Predicted and Observed Impacts during Longwall 23B (continued) SURFACE FEATURE PREDICTED IMPACTS OBSERVED IMPACTS PUBLIC UTILITIES (continued) Sewerage Pipelines Electricity Transmission Lines or Associated Plants Telecommunication Lines or Associated Plants PUBLIC AMENITIES FARMLAND AND FACILITIES Farm Buildings or Sheds Fences Farm Dams Wells or Bores INDUSTRIAL, COMMERCIAL & BUSINESS ESTABLISHMENTS AREAS OF ARCHAEOLOGICAL OR HERITAGE SIGNIFICANCE Mining induced tilt may reduce gradient of some pipes to less than that required for self-cleansing. Cracking to pipes and joints are unlikely if systematic movement occurs. Potential impacts at creek crossings where non-systematic movement is expected. Ground movements unlikely to adversely impact electrical infrastructure if systematic movement occurs. Ground movements unlikely to adversely impact telecommunications infrastructure if systematic movement occurs. Most vulnerable cables are older cables such as air pressurised lead sheathed cables. Strains may be higher where they connect to support structures or where affected by tree roots. Potential impacts to public amenities, but unlikely due to the mining of Longwall 24B. Negligible to slight impacts predicted for all farm buildings and sheds if systematic movement occurs. Potential for impacts to fences and gates. Gates are most vulnerable. Potential cracking and leakage. Ground movements unlikely to result in overflowing or reduction in dam capacity. Please refer report by Geoterra. No registered usage within SMP Area. Please refer report by Geoterra. Negligible to slight impacts predicted for all business and commercial establishments. Negligible to very impacts predicted for items of heritage significance. No impacts observed during Longwall 24B. No impacts observed during Longwall 24B. Retensioned consumer lines on Huen Pl, Pimelia St, Winpara Cl and Leiha Pl as precautionary measure. No impacts observed during Longwall 24B. No impacts observed during Longwall 24B. One impact in a semi-rural property. No impact on fences securing livestock. No impacts observed during Longwall 24B. Please refer report by Geoterra. Water depressurisation observed in water bores. Please refer report by Geoterra. No impacts observed during Longwall 24B, including Tahmoor Commercial District. No impacts observed during Longwall 24B. 22 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

24 Table 4. Summary of Predicted and Observed Impacts during Longwall 24B (continued) SURFACE FEATURE PREDICTED IMPACTS OBSERVED IMPACTS PERMANENT SURVEY CONTROL MARKS RESIDENTIAL ESTABLISHMENTS Houses, flats or units Status as at November 27 (prior to start of Longwall 24A). Retirement or Aged Care Villages Swimming Pools Associated Structures such as Workshops, Garages, On-Site Waste Water Systems, Water or Gas Tanks or Tennis Courts External Residential Pavements Fences in Urban Area Ground movement predicted at identified survey marks. Predictions and impact assessments provided for individual structures based on systematic subsidence movements. Of the 799 houses and public amenities within zone of influence of LWs 22 to 24B, 263 structures assessed to have Strain Category or 2. Potential for impacts to occur as a result of non-systematic movement. Potential for some structures to experience minor impacts that may only be classified as Tilt Category A or Strain Category. All houses expected to remain safe, serviceable and repairable provided that they are in sound condition prior to mining. Negligible to very slight impacts at Macquarie Grove Retirement Village. While predicted tilts are not expected to cause a loss in capacity, tilts are more readily noticeable in pools as the height of the freeboard will vary along the length of the pool. While predicted strains impacts are low, many of the pools are in-ground, which are more susceptible. Potential impact to pipes connected to in-ground septic tanks. Negligible impacts predicted for non-residential domestic structures, including sheds and tanks. Cracking and buckling likely to occur, though majority minor. Some fences and gates could be slightly damaged. Most vulnerable are colorbond fences. Ground movement occurred. No. of properties that have reported impacts after LW 24B = 36 (72 claims during LW 24B). No. of properties with impacts that relate to a residential structure = 2 (65 claims during LW 24B). No. of properties with impacts that only relate to associated structures = 6 (7 claims during LW 24B). No. of impacts to structures that are considered to be a result of non-systematic movements = 3. No. of impacts to structures that are considered to be a result of systematic movements = 9. No structures have been identified as being either unsafe or unserviceable at this time. However, MSB have decided that cost of repair is greater than cost of replacement for two houses. Please refer details in this report. Very slight to slight impacts observed at 3 residential structures. (These residences included in statistics for houses above). Impacts to 9 swimming pools. 6 pools have noticeable tilt. 3 in-ground pools cracked and one could not retain water. Minor impacts to 6 structures, including sheds, garages, a carport, a retaining wall and pool decking during the mining of Longwall 24B. Impacts to pavements observed on 24 properties during mining of Longwall 24B. Impacts to fences or gates observed on 4 properties. 23 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report

25 4.2. Main Southern Railway As discussed in Section 2.3, a 7 degree loss in stress free temperature was observed during the mining of Longwall 24B. In accordance with the agreed management plan with ARTC, the rail was re-stressed and restored to pre-mining condition following cessation of subsidence from Longwall 24B Roads Cracks and buckling were observed in 7 isolated locations during the mining of Longwall 24B. The impacts were minor and did not present a public safety risk. It is considered that the largest impacts were related to non-systematic movements. The impacts were repaired by the Mine Subsidence Board. A selection of photographs is provided in Fig. 4.. It is noted Longwalls 22 to 24B have directly mined beneath approximately 9.2 kilometres of public road with impacts to pavements at locations. Impact to pavement on Glenanne Place. Repaired fence and water main beneath bare patch in grass beyond. Only water main damage above longwalls to date. (Impact possibly due to anomalous non-systematic movement) Gap formed between behind kerb on Winpara Close. Size of gap not seen above longwalls in other locations (Impact possibly due to anomalous non-systematic movement) Typical impact to kerb (Patterson Street) Impact to pavement on Brundah Road (Impact possibly due to anomalous non-systematic movement) Fig. 4. Photographs of impacts to road pavements and kerbs during Longwall 24B 24 Xstrata Coal Tahmoor Colliery Report No. MSEC272-6 Longwall 24B February 28 End of Panel Report Subsidence Monitoring Report